Three dimensional mean wind flow and thickness patterns over Africa

Abstract

Conventional radiosonde wind observations and geopotential heights have been used to prepare ten-year mean motion field and thickness patterns over the African continent and its immediate neighborhood. Data for 75 radiosonde stations were used. Streamlines and isotach analyses were carried out for the six standard pressure levels of 850mb, 700mb,lOOmb during the four months of January (northern autmn) April (northern spring), July (northern summer) and October (northern autumn). The thickness for the layers 8S0-l00mb, 850-500mb and 500-l00mb were determined at each station and analyses of isopleths of thickness carried out.To obtain the divergence 'and vorticity fields, grid values of wind ,at 2.50 interval were used to compute divergence and vorticity. The relaxation method with boundary condition values as those suggested by Mukut B. Mathur (1972) were used to obtain velocity potential and str~amtunction fields from divergence and vorticity values respectively. A comparison of the meridional divergent part of the \find and zonal rotational part of the wind with the observed meridional and zonal wind components respectively is made. Spectral and harmonic analyses of the zonal and meridional_wind components and thickness values are performed.